. >> we proved the concept that you can modify the cells, infuse them back income tax patient safely, and that they live longer in the presence of h.i.v. >> reporter: as part of the study, six of the patients temporarily stopped taking their medication. in four cases, the levels of h.i.v. decreased. in one of those patients, the virus was reduced to undetectable levels. more than three years later, those modified cells continued to circulate in johnson's body and he continues to feel fine. >> it makes me want to shout out to the world that, you know, there could be an end to this. >> reporter: the main purpose of this small study was to test the safety of this new gene editing technique. so far, it does appear to be safe. the ultimate goal is to allow patients with h.i.v. to stop taking antiviral drugs but much more study is needed to know if that's possible. >> pelley: still about 1.5 million people die of aids in the world every year. jon, thanks very much. an important story. a big rewrite was announced today for the scholastic aptitude test, the s.a.t., the bane every year of 1.5